The project, to be conducted at the Boston University in the rich neuroscience community of Boston, concerns Sigma receptors, unique mammalian binding sites that modulate other neurotransmitter systems and which are richly expressed in limbic brain structures. Pharmacological studies indicate that sigma receptors modulate actions of cocaine and methamphetamine. Recently, sigma receptors also have been proposed to modulate motivating properties of ethanol, consistent with findings of sigma receptor polymorphisms in human alcoholism. Until very recently, however, the understanding of sigma receptor systems had been hampered by the unavailability of specific, subtj^je-selective ligands or of mutant mouse models that lack sigma receptor subt5T)es. Furthermore, the role of sigma receptors in voluntary intake or self-administration of ethanol are unknown. The present multipdisciplinary application uses behavioral, pharmacological, and molecular techniques to determine the modulatory role of sigma receptors on ethanol reward and reinforcement in distinct models of excessive ethanol consumption. Two models of excess ethanol intake will be studied, genetically selected alcohol-preferring rats and withdrawn outbred rats niade dependent during chronic, intermittent exposure to ethanol vapor, emphasizing positive and negative reinforcing properties of ethanol, respectively. Ethhanol self-admlnistrartation will be pharmacologically modulated (Specific Aim 1), through the administration of novel sigma receptor ligands, and molecularly (in Specific Aim 2), Through the use of sigma-1 receptor KO mice. The impact of chronic exposure to ethanol and of innate preference for ethanol on sigm receptor protein expression in discrete limbic brains regions wil lbe investigated in Specific Aim 3. impact of chronic exposure to ethanol and of innate preference for ethanol on a receptor protein expression in discrete limbic brain regions will be investigated in Specific Aim 3.